Melanoma is the most deadly form of skin cancer. Despite years of research, metastatic melanoma disease has a dismal prognosis and is often fatal (Jemal et al., CA Cancer J Clin 59:225-249, 2009). There are few therapeutic options for melanoma patients, demonstrating a need for new clinically relevant targets. Although candidate gene analyses have been powerful in identifying melanoma driver mutations (Davies et al., Nature 417:949-954, 2002; Curtin et al., J Clin Oncol 24:4340-4346, 2006; Prickett et al., Nat Genet. 41:1127-1132, 2009), no comprehensive analysis of this tumor type has yet been performed.
Glutamate antagonists have previously been shown to inhibit proliferation of human tumor cells (Rzeski et al., Proc Natl Acad Sci USA 98(11):6372-6377, 2001). Glutamate is known to activate two different types of receptors—ionotropic glutamate receptors (iGluRs) and metabotropic glutamate receptors (mGlus). iGluRs are ligand-gated ion channels that allow cations, such as calcium and potassium, to pass through the plasma membrane of the cell after being bound by glutamate. iGluRs are subdivided into three receptor types according to agonist response, one of which is N-methyl-D-aspartate (NMDA) (Hollmann and Heinemann, Annu Rev Neurosci 17:31-108, 1994). The glutamate receptor, ionotropic, N-methyl D-aspartate 2A (GRIN2A) gene encodes a subunit of NMDA receptors; the GRIN2A subunit contains the agonist binding site for glutamate (Johnson and Ascher, Nature 325:529-531, 1987).
Prior studies have suggested that transformation/transcription domain-associated protein (TRRAP) may function as an oncogene in pancreatic cancer (Loukopoulos et al., Cancer Sci 98(3):392-400, 2007; Bashyam et al., Neoplasia 7(6):556-562, 2005). TRRAP is an adaptor protein found in various multiprotein chromatin complexes with histone acetyltransferase activity, which in turn is responsible for epigenetic transcription activation. TRRAP plays a central role in the transcriptional activity of p53, c-Myc, E2F1 and other transcription factors (McMahon et al., Cell 94:363-374, 1998; Barley et al., Mol Cell 8:1243-1254, 2001). TRRAP knockout mice are embryonic lethal suggesting that TRRAP is essential for cell survival (Herceg et al., Nat Genet. 29:206-211, 2001).